Editor’s note: Kelly R. Jackson’s Garden Corner column is taking on a new format. He now takes questions called into his phone recently at the Christian County Extension Office and answers them in the column.
Question. I have an established row of boxwood that has large areas that have turned brown and appear to be dying. Some look worse than others, but the brown all appears to be on one side. What do I do next?
Answer. There are three or four possibilities to what could be happening to your boxwoods. First, like the crape myrtle and knock-out roses, the winter injury was very severe to many plants. The die-back could just be a delayed response to winter injury and as long as the damage is a small section, just prune out the dead and wait for new growth. Occasionally we get calls about pets urinating on shrubs which can cause sections of boxwoods to die. But that usually occurs to a single plant and not an entire row and the damage is typically mid-way up the plant (depending on the size of the dog). There are a couple of diseases to consider. Volutella Blight is a common fungal disease that is most noticeable in the spring when tips of branches turn red, then bronze and yellow. Pruning to improve air circulation and fungicide sprays will help. A boxwood disease called, Boxwood Blight, is new to Kentucky as of last year. This fungus causes dark circular leaf spots to develop followed by rapid defoliation of plants. Fungicide treatments and resistant cultivars are available. If it sounds like a fungal issue instead of pet or weather, bring several branch samples to the extension office for diagnosis.
Q. We have a big black cherry tree in our backyard with numerous leaves turning yellow and dropping off. There are spots all over the leaves. I’m very concerned the tree is dying or will die if it continues to lose leaves this early. Also I’m not ready to start raking leaves.
A. Trees shed leaves for many reasons. One is that the tree produced too many leaves in spring and leaves are dropped when weather is hot and dry and the tree needs to compensate for water loss from leaves. Leaves may also be shaded in the canopy and are not aiding in photosynthesis causing them to drop. Trees may also be recovering from pruning or other stressors. If the leaves are diseased, they may also be shed because they are not functioning properly. In your case, cherry trees can get a leaf spot disease called Coccomyces. It forms small spots on the leaves in early summer that are purple to reddish-brown. As the season progresses, more spots develop. Infected leaves turn yellow and fall prematurely. Don’t be overly concerned about the health of the tree however. Trees can also lose up to 10-15% of their leaves without any harmful effects. Fungicide treatments are available for this particular disease but application to a big tree is difficult for a homeowner. Try to rake and destroy the fallen leaves to help break the lifecycle of the fungus.
Q. I can see wasps or hornets going into the eaves and the siding of my house and my garage. There seem to be many points of entry and many wasps going in and out. Are they damaging my house? How can I get rid of them?
A. Wasps and hornets behind the siding are not likely causing damage to your home, but you probably still want to eliminate them and seal up any entry points. Wasp sprays are seldom effective against these nests because the nest is often located some distance from the entrance and the spray never reaches the core of the nest. Insecticidal dusts are effective when blown into the opening but the most widely available dust, Sevin, cannot be legally used in structures because it is not approved on the label. Your best option is to contact a pest control company to come destroy the hornets. Never plug the outside opening of these nests because this will force the wasps to chew their way into the interior of the house.
Kelly R. Jackson is the Christian County Extension Agent for horticulture. He can be reached at 270-886-6328 or visit Christian County Horticulture online at www.christiancountyextension.com.